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Lind, D. L.

Publications and source records attributed to Lind, D. L..

15 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1993

Experimental technique to investigate the interstellar gas - Preliminary analysis

The Interstellar Gas Experiment (IGE) exposed thin metallic foils to collect neutral interstellar gas particles. These particles penetrate the solar system due to their motion relative to the sun. Thus, it was possible to entrap them in the collecting foils along with precipitating magnetospheric and perhaps some ambient atmospheric particles. For the entire duration of the Long Duration Exposure Facility mission, seven of these foils collected particles arriving from seven different directions as seen from the spacecraft. In the mass spectrometric analysis of the noble gas component of these particles, we have detected the isotopes of He-3, He-4, Ne-20, and Ne-22. In the foil analyses carried out so far, we find a distribution of particle arrival directions which shows that a significant part of the trapped particles are indeed interstellar atoms. The analysis needed to subtract the competing fluxes of magnetospheric and atmospheric particles is still in progress.

Lind, D. L.↗
NASA NTRS1993

The Interstellar Gas Experiment: Analysis in progress

The Interstellar Gas Experiment (IGE) exposed thin metallic foils aboard the LDEF spacecraft in low Earth orbit in order to collect neutral interstellar particles which penetrate the solar system due to their motion relative to the sun. By mechanical penetration these atoms were imbedded in the collecting foils along with precipitating magnetospheric ions and, possibly, with ambient atmospheric atoms. During the entire LDEF mission, seven of these foils collected particles arriving from seven different directions as seen from the spacecraft. After the foils were returned to Earth, a mass spectrometric analysis of the noble gas component of the trapped particles was begun. The isotopes of He-3, He-4, Ne-20, and Ne-22 were detected. We have given a first account of the experiment. In order to infer the isotopic ratios in the interstellar medium from the concentrations found in the foils, several lines of investigation had to be initiated. The flux of ambient atmospheric noble gas atoms moving toward the foils due to the orbital motion of LDEF was estimated by detailed calculations. Any of these particles which evaded the baffles in the IGE collector could be entrapped in the foils as a background flux. However, the calculations have shown that this flux is negligible, which was the intent of the experiment hardware design. This conclusion is supported by the measurements. However, both the concentration of trapped helium and its impact energy indicate that the flux of magnetospheric ions which was captured was larger than had been expected. In fact, it appears that the magnetospheric particles constitute the largest fraction of the particles in the foils. Since little is known about this particle flux, their presence in the IGE foils appears fortunate. The analysis of these particles provides information about their isotropic composition and average flux.

Buehler, F.↗
NASA NTRS1992

The interstellar gas experiment: Analysis in progress

The interstellar gas experiment (IGE) exposed thin metallic foils in order to collect neutral interstellar particles which penetrate the solar system due to their motion relative to the sun. These atoms were entrapped in the collecting foils along with precipitating magnetospheric ions and with ambient atmospheric atoms. For the entire duration of the LDEF mission, seven of the foils collected particles arriving from seven different directions as seen from the spacecraft. In the mass spectrometric analysis of the trapped noble gas component, we detected the He-3, He-4, Ne-20, and Ne-22 isotopes. In order to infer the isotopic ratios in the interstellar medium from the measured concentrations found in the foil piece, several lines of investigation had to be initiated. The flux of incident noble gas atoms from the ambient atmosphere was estimated by detailed calculations. The contributions proved to be negligible, supporting the experimental evidence. Foil and machine backgrounds for the four isotopes which were measured had to be assessed individually. While this was easy for He-4, spurious foil background of He-3 had to be monitored carefully by analyzing unflown foil pieces. Trapped Ne concentrations are not far above the background. During the flight, a stuck electrical relay precluded the foil-trays from sequencing as designed. Therefore, we could not use the seasonal variation of the direction of the incoming interstellar atoms to make the distinction between interstellar and magnetospheric components of the trapped particles. Instead, we had to try the method of stepwise heating to extract the interstellar component at lower temperatures than we use to extract the magnetospheric component (the interstellars hit the foil with lower energies than most of the magnetospherics). New limiting values for the isotopic composition of the interstellar medium, unavailable yet from any other method of measurement, are emerging from this analysis.

Buehler, F.↗
NASA NTRS1992

The interstellar gas experiment

The Interstellar Gas Experiment (IGE) exposed thin metallic foils to collect neutral interstellar gas particles. These particles penetrate the solar system due to their motion relative to the sun. Thus, it is possible to entrap them in the collecting foils along with precipitating magnetospheric and perhaps some ambient atmospheric particles. For the entire duration of the Long Duration Exposure Facility (LDEF) mission, seven of these foils collected particles arriving from seven different directions as seen from the spacecraft. In the mass spectroscopic analysis of the noble gas component of these particles, we have detected the isotopes of He-3, He-4, Ne-20, and Ne-22. In the foil analyses carried out so far, we find a distribution of particle arrival directions which shows that a significant part of the trapped particles are indeed interstellar atoms. The analysis needed to subtract the competing fluxes of magnetospheric and atmospheric particles is still in progress.

Lind, D. L.↗
NASA NTRS1984

Interstellar-gas experiment (A0038)

The objectives of this experiment are to collect and isotopically analyze interstellar gas atoms around the orbit of the Earth for the purpose of obtaining new data relevant to understanding nucleosynthesis, and to study the dynamics of the interstellar wind inside the heliosphere and the isotopic composition of the interstellar medium outside the heliosphere. The experiment hardware will act as a set of simple cameras with high-purity copper-beryllium collecting foils serving as the film. The experiment housing will mount and thermally control the foils, establish the viewing angles and viewing direction, provide baffling to reject ambient neutral particles, provide a voltage grid to reject ionospheric charged particles, sequence collecting foils, control exposure times, and protect the foils from contamination during the deployment and retrieval of the LDEF. After being returned to Earth, the entrapped atoms can be analyzed by mass spectroscopy to determine the relative abundance of the different isotopes of helium and neon. An attempt will also be made to detect argon.

Lind, D. L.↗
NASA NTRS1979

Solar and terrestrial noble gases in magnetospheric precipitation

Metal-foil collectors were installed on the external structure of Skylab to entrap precipitating magnetospheric particles. The foils were retrieved, and the entrapped helium, neon, and argon were isotopically analyzed in a high-resolution mass spectrometer. Solar and terrestrial helium and neon and terrestrial argon were detected. As expected, the isotopic composition of neon and argon in the high atmosphere was found to be strongly fractionated. Special techniques were used to estimate the initial particle energy of He-3. The measured He-3 flux is consistent with the assumption that precipitating solar He-3 is the major source of terrestrial He-3.

Lind, D. L.↗
NASA NTRS1974

Magnetospheric particle composition experiment

Thin foils of aluminum and platinum were mounted on the exterior of the Skylab spacecraft where they were bombarded by particles that penetrate to the 400-km spacecraft altitude, including auroral particles precipitating from the earth magnetosphere. These foils have a high trapping efficiency for both charged and neutral particles above 1 keV and a decreasing but appreciable efficiency below that energy. Some sections of the foils were double layered to obtain an estimate of the energy of the entrapped particles. The foils were retrieved and returned for analysis in an ultrahigh-vacuum mass spectrometer. So far, the noble gas components of the entrapped particles have been analyzed in selected sections of two foils. Helium-4, helium-3, neon-20, and neon-22 have been detected.

Geiss, J.↗
NASA NTRS1973

Electron observations in the solar wind and magnetosheath.

Electron temperature measurements taken by a triaxial electron analyzer on Ogo 5 in the solar wind and in the magnetosheath are interpreted. In the interplanetary medium, observations made on the bow shock connected lines of magnetic force have been separated from those made on non-bow-shock connected lines. The dependence of electron thermal properties on the local field geometry is discussed together with features of electron temperature and density discontinuities across the bow shock. The velocity distribution function is characterized together with temperature and density variations in a part of the dawn magnetosheath.

Scudder, J. D.↗
NASA NTRS1965

A triaxial electron detector

Triaxial electron detector for use in sounding rocket experiment to study polar cap absorption

POLAR CAP ABSORPTION↗